METHOD FOR MONITORING THE ROTATIONAL SPEED OF A ROTOR OF AN ELECTRIC TRACTION MOTOR IN A MOTOR VEHICLE

Abstract

The invention relates to a method for monitoring the rotational speed of a rotor of an electric traction motor (18) of a motor vehicle (10) comprising a powertrain comprising the electric traction motor, a train (12) which can be coupled to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), the method comprising steps of: a) Receiving a wheel rotational speed value from the ABS / ESP computer; b) Determining a rotor rotational speed value of the electric traction motor from the received wheel rotational speed value; c) Estimating an overspeed condition of the electric traction motor from the previously determined rotor rotational speed value; and d) If an overspeed condition is detected, triggering an associated degraded mode operating configuration of the powertrain. (Fig. 1)

Description

Title of the invention: Method for monitoring the rotation speed of a rotor of an electric traction motor in a motor vehicle Technical field of the invention

[0001] The invention relates, in general, to the technical field of monitoring the operation of an electric traction motor within an electric motor vehicle. In particular, the invention relates to a method for monitoring the rotational speed of a rotor of an electric traction motor, in particular of an electric traction motor driving a rear axle of an electric motor vehicle known as AWD (acronym for "All Wheel Drive" in English terminology meaning "all-wheel drive"). State of the prior art

[0002] Today, a rotational speed of an electric traction motor rotor is measured and monitored via a rotational speed sensor fitted to the rotor. The purpose of this measurement and monitoring is to compare the measured rotational speed with a maximum rotational speed that the rotor must not exceed during operation of the electric traction motor. In the event that the maximum rotational speed is exceeded, an alert is issued and a degraded operating mode of the powertrain is implemented.

[0003] However, the rotation speed sensor fitted to the rotor lacks precision. In fact, it only has three notches uniformly distributed around a circumference of the rotor. This does not allow for a precise measurement of the instantaneous rotation speed of said rotor thus equipped. Statement of the invention

[0004] The invention aims to remedy all or part of the drawbacks of the state of the art by proposing in particular a solution allowing precise measurement and monitoring of the instantaneous rotation speed of a rotor of an electric traction motor driving a train of an electric motor vehicle.

[0005] To do this, according to a first aspect of the invention, a method is proposed for monitoring the rotational speed of a rotor of an electric traction motor of a motor vehicle comprising a powertrain comprising the electric traction motor, a train coupled to the powertrain, wheels associated with the train and an ABS / ESP computer, the method comprising steps of: a. Receiving a wheel rotational speed value from the ABS / ESP computer; b. Determination of a value of rotation speed of the rotor of the electric traction motor from the received value of rotation speed of the wheels; c. Estimation of an overspeed condition of the electric traction motor from the previously determined rotor rotational speed value; and d. If an overspeed condition is detected, triggering of an associated powertrain degraded mode operation configuration.

[0006] According to one embodiment, the overspeed state is estimated relative to a predetermined threshold value of maximum rotational speed of the rotor.

[0007] According to one embodiment, during step c), the method estimates whether the rotor rotation speed value thus determined is within a range delimited by the predetermined threshold value and a value equal to the predetermined threshold value multiplied by a predetermined speed coefficient, and associates it with a duration of presence in this range.

[0008] According to one embodiment, during step d), if the rotation speed value is in the range for a time less than a predetermined threshold time value, then the method triggers an operating configuration in which it sends a reduced torque setpoint to the powertrain.

[0009] According to one embodiment, during step d), if the rotation speed value is in the range for a time greater than a predetermined threshold time value, then the method triggers an operating configuration in which it switches off the electric traction motor and possibly decouples the powertrain from the train.

[0010] According to one embodiment, during step d), if the rotation speed value is greater, in absolute value, than a value equal to the predetermined threshold value, in absolute value, multiplied by a predetermined speed coefficient, then the method triggers an operating configuration in which it switches off the electric traction motor and possibly decouples the powertrain from the train.

[0011] According to one embodiment, during step c), the method differentiates between a forward overspeed state and a reverse overspeed state.

[0012] According to one embodiment, the method comprises a preliminary triggering step in which steps a) to d) are carried out if the electric traction motor is in operation.

[0013] According to one embodiment, during the preliminary step, the method checks whether the powertrain is coupled to the train.

[0014] According to yet another aspect of the invention, there is provided a motor vehicle comprising a powertrain comprising an electric traction motor, a train coupled to the powertrain, wheels associated with the train and an ABS / ESP computer, as well as a computer arranged to implement a monitoring method having one of the preceding technical characteristics. brief description of the figures

[0015] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate: • [Fig.l]: schematic view of an AWD electric motor vehicle implementing a monitoring method according to the invention. DETAILED description of an embodiment

[0016] [Fig.l] schematically illustrates an electric motor vehicle 10 AWD. It comprises a front axle 10 driven by a front powertrain 13 comprising an electric machine or front traction electric motor 15 and a reduction gear 16 connected via front transverse transmissions to the front wheels 11.1 and 11.2. A power supply interface 24 makes it possible to connect the front traction electric motor 15 to a traction battery 23. In addition, a computer 26, connected to the front traction electric motor 15, makes it possible to control the front powertrain 13.

[0017] On the other hand, the AWD electric motor vehicle comprises a rear axle 12. The rear axle 13 is driven by a rear powertrain comprising an electric traction motor or rear electric machine 18, a reducer or gearbox 19 and a dog clutch system 21 of the rear powertrain making it possible to dog-clutch or undog-clutch the rear powertrain of the rear transverse transmissions which are connected to the rear wheels 12.1 and 12.2. A power interface 25 makes it possible to connect the rear traction electric motor 18 to the traction battery 26. The computer 26 is connected to the rear traction electric motor 18 on the one hand, and, on the other hand, to the dog clutch system 21 in order to control the rear powertrain of the electric motor vehicle 10.

[0018] The dog clutch system 21 makes it possible, in particular, not to drive the rear powertrain in rotation when the electric motor vehicle 10 is operating in “4x2” mode (that is to say that only the front powertrain 12 is used to move said electric motor vehicle 10 forward) and thus to reduce friction losses of the electric motor vehicle and thus save energy from the traction battery 26, but also to avoid generating electrical energy at the poles of the electric traction motor 18 which could lead to a stator catching fire, due to the failure to be able or able to evacuate this electrical energy.

[0019] Furthermore, in a manner known per se, the electric motor vehicle 10 comprises an ABS / ESP computer 30 (ABS is the Anglo-Saxon acronym for “Anti-Blocking System" or anti-lock system, and ESP is the Anglo-Saxon acronym for "Electronic Stability Program" or electronic stability program, also called electronic trajectory corrector). In order to operate, the ABS / ESP computer 30 continuously receives speed information from wheel speed sensors 31, 32, 33, 34, here four in number and associated respectively with the wheels 12.1, 12.2, 11.1, 11.2 of the electric motor vehicle 10. Each wheel speed sensor 31 to 34 comprises an angular encoder which measures the angular displacement of the associated wheel. Knowing a development of said associated wheel, the ABS / ESP computer 30 deduces a speed of the electric motor vehicle 10. The angular encoder comprises a toothed wheel or target integral in rotation with the wheel and a reader which detects a passage of the teeth of the target.Knowing the number of teeth of the target distributed uniformly on a circumference of the latter, the ABS / ESP computer 30 estimates the distance traveled by the wheel, a distance which, integrated into a time, makes it possible to know the speed of the electric motor vehicle 10 at the wheel in question. To ensure safe and optimal operation of the ABS / ESP system of the electric motor vehicle 10, the wheel speed sensors 31 to 34 are very precise, because the target has a number of teeth much greater than the three notches of the speed sensor of the rotor of the electric traction motor 15 or 18.

[0020] The calculators 26 and ABS / ESP 30 are connected to each other so as to be able to exchange information.

[0021] We will now describe in detail a method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention. We will illustrate the point with regard to the rear axle 12 of the electric motor vehicle 10.

[0022] Firstly, the computer 26 receives speed information, “VvhlAR”, of the rear wheels 12.1, 12.2 from the ABS / ESP computer 30. On the other hand, it receives information concerning the state of the dog clutch system 21, “Ecrabot”.

[0023] In addition, the computer 26 receives current information, “ImelAR”, at the power supply terminals of the power supply interface 25, therefore of a current level consumed by the electric traction motor (when it operates in motor mode) or of the current level produced by the electric traction motor to be stored in the traction battery 23 (when it operates in generator mode).

[0024] On the other hand, the calculator 26 has a value of the wheel development (Droue) and a value of a reduction gear ratio (Dred) of the reduction gear 19. These two values ​​are recorded in a memory during a development of the method for monitoring the rotation speed of a rotor of an electric traction motor according to the invention.

[0025] It should be noted that the method of monitoring the rotational speed of a rotor of a electric traction motor according to the invention is only operational: • When the rear traction dielectric motor 18 is in operation (either in motor mode or in generator mode), that is to say when an absolute value of current ImelAR consumed or produced at the terminals of the power supply interface 25 is greater than a predetermined threshold, Slmax. For example, Slmax is of the order of magnitude from 5A to 10A; and, • When the dog clutch system 21 is in the dog clutched position, i.e. if Ecrabot = “dog clutched”.

[0026] Once operational, the method for monitoring the rotation speed of a rotor of an electric traction motor according to the invention calculates a rotation speed of the rotor, “WmelAR”, of the rear electric traction motor 18 from the previous information received, namely: WmelAR = VvhlAR x 1000 x Dred / Rroue / 60. The value of VvhlAR is positive when the electric motor vehicle is in forward gear and negative when the electric motor vehicle is in reverse gear.

[0027] Then, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention carries out the following steps according to the value of VvhlAR.

[0028] If the value of VvhlAR is positive, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention verifies that the value of WmelAR calculated previously is less than a predetermined threshold of maximum rotational speed in the forward direction (SWmaxAV). A value of SWmaxAV is calibratable when developing the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention and has a value which depends on the architecture of the rear electric traction motor 18, for example around 15,000 rpm (the value is positive, because it is in the forward rotational direction of the electric motor vehicle).If, on the contrary, WmelAR is greater than SWmaxAV, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention checks whether the value of WmelAR is in a range [SWmaxAV; CoefWAV x SWmaxAV] for a duration less than DAV, where DAV is a maximum overspeed time threshold in the forward direction of the electric motor vehicle and calibratable during the development of the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention and having a value which depends on the architecture of the rear electric traction motor 18, for example 120 seconds, and where CoefWAV is a predetermined forward overspeed coefficient, of the order of 1.2 for example. In this case, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention. engages a first operating configuration of the rear powertrain. If the duration is greater than DAV, then the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention engages a second operating configuration of the rear powertrain. Finally, if the value of WmelAR is greater than CoefWAV x SWmaxAV, regardless of the duration, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention engages a third operating configuration of the rear powertrain. The different operating configurations will be described in detail later.

[0029] If the value of VvhlAR is negative, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention verifies that the previously calculated value WmelAR is indeed greater than a predetermined threshold of minimum rotational speed in the reverse direction (SWmaxAR). A value of SWmaxAR is calibratable when developing the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention and has a value which depends on the architecture of the rear electric motor 18, for example around -13,500 rpm (the value is negative, because it is in the reverse rotational direction of the electric motor vehicle).If, on the contrary, WmelAR is less than SWmaxAR, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention verifies whether the value of WmelAR is in a range [CoefWAR x SWmaxAR; SWmaxAR] for a duration less than DAR, where DARV is a maximum overspeed time threshold in the reverse direction of the electric motor vehicle and calibratable during the development of the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention and having a value which depends on the architecture of the rear electric traction motor 18, for example 100 seconds, and where CoefWAR is a predetermined overspeed coefficient in reverse, of the order of 1.15 for example.In this case, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention engages a fourth operating configuration of the rear powertrain. If the duration is greater than DAR, then the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention engages a fifth operating configuration of the rear powertrain. Finally, if the value of WmelAR is less than CoefWAR x SWmaxAR, regardless of the duration, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention engages a sixth operating configuration of the rear powertrain. The different configurations are described in detail below.

[0030] Therefore, as long as the value of WmelAR is between SWmaxAR and SWmaxAV, the method for monitoring the rotation speed of a rotor of an electric traction motor according to the invention considers that the rotation speed of the rotor is not judged to be “overspeed”, and does not engage any of the aforementioned operating configurations: the rear powertrain then operates normally, in non-degraded mode.

[0031] Concerning the various aforementioned configurations, the first configuration, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention reduces a torque setpoint to the rear powertrain by the order of a progressive coefficient depending on the coefficient of exceeding the maximum speed of the rotor: if the rotational speed of the rotor exceeds by 10%, the maximum speed of the rotor (SWmaxAV), the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention reduces the torque setpoint by 10% multiplied by a safety coefficient (which can be around 2), i.e. a reduction of 20%. A service indicator light is lit on a dashboard of the electric motor vehicle, to signal to a user an anomaly on the powertrain and encourage said user to go to the after-sales network to carry out a check.A fault code is generated to signal to the after-sales service that the rear electric motor 18 has entered “minor overspeed”.

[0032] For the fourth configuration, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention reduces the torque setpoint to the rear powertrain by the order of a progressive coefficient depending on the coefficient of exceeding the minimum speed of the rotor: if the rotational speed of the rotor exceeds the theoretical minimum speed of the rotor (SWmaxAR) by 10%, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention reduces the torque setpoint by 10% multiplied by a safety coefficient (which may be around 2), i.e. a reduction of 20%. A service indicator light is lit on the dashboard of the electric motor vehicle, to notify a user of an anomaly on the powertrain and encourage said user to go to the after-sales network to carry out a check.A fault code is generated to notify the after-sales service that the rear electric motor 18 has entered "minor overspeed". This fault code may be the same as the first configuration described above or perhaps a specific fault code to differentiate between forward and reverse overspeed.

[0033] For the second, third, fifth and sixth configurations, the method for monitoring the rotation speed of a rotor of an electric traction motor according to the invention cuts the power supply to the rear electric motor 18 to turn it off and controls the rear dog clutch system 21 so that it goes into the disengaged state. service indicator light is lit on the dashboard of the electric motor vehicle, to signal to a user an anomaly on the powertrain and encourage said user to go to the after-sales network to carry out a check. A fault code is generated to signal to the after-sales service that the rear electric motor 18 has entered “major overspeed”. This fault code is necessarily different from the fault code of the first and fourth configurations previously described.

[0034] In alternative embodiments, the second, third, fifth and sixth configurations may be different from each other so that they can be differentiated, in particular by after-sales service.

[0035] In all cases, the preceding configurations are configurations corresponding to degraded modes of operation of the rear powertrain.

[0036] Furthermore, the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention comprises a step of restoring the rear powertrain to normal operating mode. This restoration is done when the ignition is switched off (pressing a START / DEMARRER button or operating an ignition key), that is to say that the fault is rehabilitated and the electric motor vehicle is authorized to set off again with all its functions restored: the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention turns off the service indicator light previously lit and authorizes the operation of the rear electric motor 18 and the dog clutch thereof with the rear running gear 12 by the dog clutch system 21. The fault code remains stored in the computer 26 for after-sales service.But this fault code does not remain in a "permanent" state in the memory of the calculator26, but the fault code goes into a "transient" state to indicate to the after-sales service that the fault has resolved itself.

[0037] It is clear from the above that the implementation of a method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention makes it possible to avoid damage to the rear electric motor that could lead to it catching fire. Also, the implementation of the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention makes it possible to limit the risk of fire and breakage of the rear electric motor and therefore makes it possible to secure the users of the electric motor vehicle 10 AWD. Consequently, the implementation of the method for monitoring the rotational speed of a rotor of an electric traction motor according to the invention makes it possible to avoid changing the rear electric motor in the event of “overspeed” of rotation of the rotor of said rear electric motor.

[0038] It should be noted that the method of monitoring the rotational speed of a rotor of a The electric traction motor according to the invention just described is applicable both in electric motor vehicles and hybrid motor vehicles. It is applicable to any AWD motor vehicle having an electric powertrain on their rear axle to be able to switch to 4x4 or AWD mode.

[0039] Naturally, the invention is described in the foregoing by way of example. It is understood that the person skilled in the art is able to carry out different variant embodiments of the invention without departing from the scope of the invention.

[0040] It is emphasized that all features, as they emerge for a person skilled in the art from the present description, the drawings and the attached claims, even if concretely they have only been described in relation to other determined features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or meaningless.

Claims

Claims

1. Method for monitoring the rotational speed of a rotor of an electric traction motor (18) of a motor vehicle (10) comprising a powertrain comprising the electric traction motor, a train (12) coupleable to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), the method comprising steps of: a. Receiving a wheel rotational speed value from the ABS / ESP computer; b. Determining a rotor rotational speed value of the electric traction motor from the received wheel rotational speed value; c. Estimating an overspeed condition of the electric traction motor from the previously determined rotor rotational speed value; and d. If an overspeed condition is detected, triggering an associated degraded mode operating configuration of the powertrain.

2. Method according to claim 1, characterized in that the overspeed condition is estimated relative to a predetermined threshold value of maximum rotational speed of the rotor.

3. Method according to claim 2, characterized in that, during step c), the method estimates whether the rotor rotation speed value thus determined is included in a range delimited by the predetermined threshold value and a value equal to the predetermined threshold value multiplied by a predetermined speed coefficient, and associates it with a duration of presence in this range.

4. Method according to claim 3, characterized in that, during step d), if the rotational speed value is in the range for a time less than a predetermined threshold time value, then the method triggers an operating configuration in which it sends a reduced torque setpoint to the powertrain.

5. A method according to claim 3, characterized in that, in step d), if the rotational speed value is in the range for a time greater than a predetermined threshold time value, then the method triggers an operating configuration in which it turns off the electric traction motor and possibly decouples the powertrain from the train.

6. Method according to claim 2, characterized in that, during step d), if the rotation speed value is greater, in absolute value, than a value equal to the predetermined threshold value, in absolute value, multiplied by a predetermined speed coefficient, then the method triggers an operating configuration in which it switches off the electric traction motor, and possibly decouples the power unit from the train.

7. Method according to one of claims 1 to 6, characterized in that during step c), the method differentiates between a state of overspeed in forward gear and a state of overspeed in reverse gear.

8. Method according to one of claims 1 to 8, characterized in that the method comprises a preliminary triggering step in which steps a) to d) are carried out if the electric traction motor is in operation.

9. Method according to claim 8, characterized in that, during the preliminary step, the method verifies that the powertrain is coupled to the train.

10. Motor vehicle (10), characterized in that it comprises a powertrain comprising an electric traction motor (19), a train (12) coupleable to the powertrain, wheels (12.1, 12.2) associated with the train and an ABS / ESP computer (35), characterized in that the motor vehicle comprises a computer arranged so as to implement a monitoring method according to one of claims 1 to 9.

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